Transmission system employing pulse modulation



Sept. 7,

1943. w. A. BEATTY TRANSMISSION SYSTEM EMPLOYING PULSE MODULATION Filed May 8, 1940 Fig. 1.-

use @ffm/aes, F13-2' Lec-naad afa/v fiese r 'I Fig. 2 shows three target Aplate 4shown 'in Fig. 2; and

Patented Sept.v 7,

I 'PULSE William Arnold Beatty, Sidcup, 'El'lglan'd,` assigner to International( `StandardA tion, New York,N. Y.

,a Application Mays,1940,seriaiNoJssaeisf, c In'Grea-tritain May30,19 39` vfciaims. (C1.25oj- 9jj1"r This invention relates to radio .transmission A systems utilising pulse .modulation inavplurality of channels, and residesin a systemwhereinjthe .fixed edges of the basic .time-modulatedpulses for; .the dierent channels are synchronised. The invention is applicablegto twofwayoommunication ,systems and to systemsemploying. a

rectangular 4pulsesllloccurling atequaltirnef intervals having a duration AQfv 'f. the 1.111%? 14' valfbetvveen consecutive pulses.v 4Theirequ'en`cyi of `occurrence -canzlce,for example, .20,006v` `per .q

`nunfiloer of transmitter-receivers, as.; wellas to transmitters single or multiple operating simultaneously on different wavelengths.

In' copending United States Patent No 2,256,336, issued September 16, 1941, for Pulse modulation system and application Ser. No.,

312,645, filed January 6, 1940 for Electric signa1- ling systems, there are described methods of generating pulses which are suitable for pulse jl i) modulation'. The former describes methods of generating. pulses coded as S/RT and S/RL, while the latter describes lnethods'of generating pulses .coded as RT-l-S/RT and RL|S/'RL.

Throughout-thefollowing description A HTTPS/RTA pulses nu befcnsidered A.as also 'ihiudirfig RL-- S/RL pulses, as both types are similarin essential 'characteristics l v In an RT|S/RT pulse gence to amplitude modulated receivers,- also supplies timing for the insertiongof pulses .correspending to the trailing edges of the combined RTli-S/RT pulses, these trailing edges occurring at equal time intervals, f The presentinvention; deals especially -vvith methods ofV utilising one timing pulse train for more than one transmission system having ,S/RT pulses. time modulated in accordance Withfintelligence The. timing pulse trainJnay beg system the RTportion `-of thepulse, irradditionv to supplying intellior may bel time modulated and combined With an S/RT pulse giving an RT-l-S/RT; pulse, or thetirning pulse may be unn'ioduiatedl as regards time.- f-

Various aspects of the invention are set `out in .the appended claims. v rI he accompanying drawing serves to illustra-te certain features of the proposal, .In the drawing:

Fig. 1 shows `a rectangular pulseutilised, for l synchronising transmitters and receivers;

arrangements for pulse generators; l.

Fig'. 2A is a .partial diagrammatic vie\v illus trating a modified arrangement table used in connection with thev target plate; arrangement Electric Corporal'igQ Y3 l shovvs in pulse transmitters.

`Referring to Fig. l, there fis` shown 1a t1 second. Y'I 'he leading edges 2220i' thepuls are used to synchronise a saW-tooth'WaVefiorm generator Whichis usedfor 'thedeflection oi' an electron .beam of 'an 'SYRT type. Pulse generatori yL 23 Figi 2, as described and shownin,.ligs'.-1,'2, 3

also used.- tofsuppressl the electron beam during the. yback mentioned v Patent No. 2,256,336.

. r"Referring to Fig. 2 ofthe` presentinvention, there are shown two other `pulserv generator'rcollector. plate Yarrangeinents 2d and 2 5, Whichare similar to the 'arrangement 23.

be made vtosynchronise independentisaW-tooth generators` foreach; pulse generator: The beams f in the. various pulse generators are independently-deflected in directions at right anglesjtoj. the y 'deflection due to thesaW-tooth Wave-fo-rrn by' signals `corresponding t0 three independntkinds of intelligence, for instance, threejtelephone messages, thereby generating three'independei 1t groups of S/RT pulses'which are ,cl1a1'acte1istic of-rthree different kinds of intelligence.

yThe pulse` 2| in. addition Vto synchronizing.` the generation of vthevariousfgroups ofS/Rfpulses f is .utilised to` modulate a transmitterZ .Fig:3, 1. v K which, for example, can radiate` on a Wavelength of 8 metres.. v'I'he S/ RTpulses derived 'fromithe Y plates 23, 2d and 25. can be utilised to modulate f i the transmitters'l, 28 and 29 respectively which, f for eXample,'.can radiate on 135,*"2'and1i2.5` lmetres respectively, 'i 7 ...Ata receiving location remote from'rtheitrans# 'mitters 26,21, 28"and. 2Q; areceiverj (not shown) capable of receiving the transmission `on'qandl1.*75rnetres."isfprovi'ded. The leading edges-22 -of the' pulses-2l onthe 8 metre transmissionare utilised to give thefixed edge pulses of adouble `pulsemodulation system, while the Sf/RTj-pulses vof the v 1.75 metre'transmission supplythe Varig 'able edge Ipulsesofd the same doublepulsgmodulation system. In anyknownsmannerthevariable edge pulses andthe fixed edge; puls yn ovv-.b-e utilised to supply-intelligence".corres s trolre,V as describedin .'tlie. above The sawtooth Waverform used for deflectingthe beanrfacross the target 23 can also bejused`to-deflectinde;- pendent velectron beams across .each` of the {tar-k gets24 and 25, or alternatively' the pulses2i can short wave transmitter working for insta-nce onf This latter transmission h fow b f 1.9 metres.

geese/i4 Y necessarily constant carrier frequency, the pulse trains being unintelligible without information as to their manner of use.

received at the original transmitting "looationI and as already described the S/RT pulse modu- Y lation can be utilised to giveiritfelligern;'e'similar.` a i* u i synchronisation may in some cases be eli'ected di- .to that causing the generation of the S/RT pulses at the remote location.

In a similar manner the trans'missionsradiated i by the .transmitters 28 and 29 canbereceived at other locations, and Aif desired, two-Way "communication can also beestablishedbetween thesev pointsand 'the joriginal transmitting station:v Y It should be obvious from the foregoing thatl it is not essentialV for jth-"e transmitter 26 to be "located in the sameplace as the transmitters 2l, Ejand V29, fand that two-Way communication can beV established between any `tvvo Alocations, -provided thegeneration of Ithe -S/RT pulses -is madev dependent upon the time tof-occurrence of the pulses 2|. j j

, YOne reasonfor keeping Ith'epulses 2i of a relatively short vdurati'onis that lthese pulses can be utilised to give electron beam suppression duringthe iiyback strokes or `the saw-tooth waveform signals used jfor deiiecting-the beam-'inthe i various pulse generators, andprovided that fin the case under consideration the iiyback isv less ythan 5% `of `the total Waveform duration, it would be adisadvantage'to makethe Apulse 21 anylonger initsduraticn,as lthen portions of thefo'rward stroke Vof the savv-tootl'il signals would beun- -f necessarily suppressed with the resul-t tliatthe` intervals'between pulses would fle made unnecessarily-large. i

Way communication 'it is not necessary for the I pulse radiated by "the, transmitter yZG'ft-o be of shortduration, theonlyiessentials being that -the pulses have the sam-e ffrequency Vof-oc'cufrreno'e 'as the pulses 2l and have'one edge ioccurring'at equal time intervals. The pulses 'radiated from the transmitter4 26 can-be time modulated-in accordanoe with 'intelligence 'and Camif-or instance, be RT or RL -pulses as described in the *above mentioned Patent No. 2,256,336, for vcan be RT-i- 't5/RT or RL-l-S/RLipulses as described Yin Application -Ser..fNo. S12-,645. lSuch an alternative larrangement has been d iagrammatically indicated in Fig. 2A, showinga source ofpulses ofvariable duration connected to thesaw tooth Wave genera'tor` in place of the source of pulses havingone edge .occurring at equal time intervals, las illustrated in Fig. 2. i Y

Although the foregoing description yrelates to the generation of S/RT pulses, it'is'obvious that it can be applied torany pulse generating system 4'in which lineal' Ideflection of an electron beam across a target plate or other "collectoris utilised for the purpose foi generating time -modulated Vthesynchronising pulses of a vision transmission can be utilised in such a manner that they synchronise a plurality of pulse generators for the purposes described in the foregoing proposal.

It will be appreciated that a large measure of secrecy canbe attained by the invention, since detection can be made dependent upon the reception of two-pulse trains of diierentand not Although in the foregoing it has been proposed to synchronise the pulse trains of the different channels by the transmission of a marking pulse,

rectly between adjacent transmitters vand in other 'cases other methods become possible. Synchronising signals may besent by Wire at their natural frequency oras a modulation.

What is claimed is:

1. A lradio transmission system comprising at least one transmitter adapted. to transmit variable edge pulses' characteristic of a sound or like'wave, and Sanother 'transmitter adapted to transmit complementary iXed-edge pulses andmeans at a receiving pointfor combining the eiects of the t impulses from said transmitters in order toderive therefrom intelligence transmitted by one of said transmitters.

2. A radio transmission system'employingpulse modulation for transmission of telephonie-signals lor the like, 'comprising 'means for produo'ingia-series of spaced `impulses `for synchronizing purposes, a plurality of "transmitters adapted 1Ato transmit .pulse modulated signals, means for synchronizing said transmitters withsaid `spaced synchronizing impulses, whereby a component of each pulse modulated signal from the respective' transmitters has `a timer'elation fixed in .respect to said impulses, andmeans -fortransmittingsaid spaced synchronizing impulsesifo'r use in demodulating signals fromi-all of said transmitters.

, v 3. A radio transmission system according to claim 2 wherein said spaced synchronizing Limpulses have -equal durations lof th'e orderof 5% of the interval between vconse'culti-ve lones Soif-"such iimpu'ls'es.

4. A radio transmission system according to claimf2 'wherein v`said 'means for transmitting 'said'spaced synchronizing impulses vare adapted to 'transmit a '-'train of impulses having one "edge spaced at constant time Vintervals for synchronizing purposes, and further comprising lmeans 'for varying the duration ofsa'id spaced synchro- ;nizing impulses vin accordance `with la further "signaltobe transmitted.` i,

5. A- secret radio transmission system` for simultaneous `'transmission of aplurality 'of :telepho'nic signals or the likefcomprisinga plurality of .sourcesof signals, a common fsourc'eof syn- 'chronizing pulsesa vpluralityo'f pulse modulation' means for producing under the control of each oneof said sources va correspondingiseriesof'biief pulses Whose time position in 'respect 'to that .of the synchronizing .pulses from 'said source jrepresents Vthe momentary Vamplitude of the corresponding signal, means for transmitting` all of saidse'ries of pulses on .different `carrier'Wave lengths, means forfsynchronizing said plurality of pulse modulating means, whereby the time lpositions of the pulses of the respective 'Wavelengths are all relatedto -thesame 'standard of 'time positiouandrmeans for transmitting asngle series of synchronizing pulses for use Linthe demodulation of all of said first mentioned fpulses.

modulating means is located at a second'station,V

and wherein said means for synchronizing said pulse modulating means comprisesmeans rfor transmitting radio signals from said rst station to said second station.

'7. A radio receiver of the system according` to! claim 2, comprising means for receiving" said l pulse modulated signals, meansfo'r receiving vspaced synchronizing impulses, and means,y forf` demodulating said pulse modulated signals kand. said spaced synchronizing impulses in accordance `with the time relation between rsaid spaced sine s j chronizing impulses and said modulated signals.

WILLIAM ARNQLD BEATTY. 

